Electron micrograph showing the brush border of intestinal epithelial cells of the rat. The parallel microvilli of the brush border are about 0.1 µm wide and 1.0 µm in length. Image by Jean Paul Revel and Sanford Palay, Figure 38 from Chapter 2 (Specializations of the Free Surface) of 'The Cell, 2nd Ed.' by Don W. Fawcett M.D. A PDF copy of the accompanying chapter is available on the ASCB's BioEDUCATE website.